Systems and Methods for Power State Transitioning in an Information Handling System

ABSTRACT

Systems and methods for power state transitioning in an information handling system having a volatile memory and a nonvolatile memory are disclosed. Dirty data in the volatile memory may be identified. The dirty data may include data that has not been stored in the nonvolatile memory. Dirty data may be written from the volatile memory to the nonvolatile memory. Transitioning to a reduced power state may be in response to a trigger event. Transitioning from the reduced power state may be in response to a wake signal. Data may be copied from the nonvolatile memory to the volatile memory. An operating system may be waked to a restored state.

TECHNICAL FIELD

The present disclosure relates generally to information handling systemsand, more particularly, to Systems And Methods For Power StateTransitioning In An Information Handling System.

BACKGROUND

As the value and use of information continues to increase, individualsand businesses seek additional ways to process and store information.One option available to these users is an information handling system.An information handling system generally processes, compiles, stores,and/or communicates information or data for business, personal, or otherpurposes thereby allowing users to take advantage of the value of theinformation. Because technology and information handling needs andrequirements vary between different users or applications, informationhandling systems may vary with respect to the type of informationhandled; the methods for handling the information; the methods forprocessing, storing or communicating the information; the amount ofinformation processed, stored, or communicated; and the speed andefficiency with which the information is processed, stored, orcommunicated. The variations in information handling systems allow forinformation handling systems to be general or configured for a specificuser or specific use such as financial transaction processing, airlinereservations, enterprise data storage, or global communications. Inaddition, information handling systems may include or comprise a varietyof hardware and software components that may be configured to process,store, and communicate information and may include one or more computersystems, data storage systems, and networking systems.

Examples of information handling systems, including computers such asworkstations, desktop computers and portable computers, may typicallyhave a technique for limiting the amount of power consumed by thesystems. One technique may involve placing a system in one or morereduced power states. For example, a system may have standby, hibernateand shutdown processes for placing the system in corresponding reducedpower states.

Standby may involve, e.g., saving data and instructions to memory, suchas volatile memory, and transitioning to a low power state. However, asmemory densities and system capacities increase with advances ininformation handling systems, it may become increasingly important topower down volatile memory due to increasing power requirements. Oneexample of this may be the increasing power requirements associated withrefresh requirements of DRAM (dynamic random access memory).

Hibernate may involve, e.g., storing data and instructions to disk andtransitioning to a lower power state. However, having different lowpower states from which to select, such as standby, hibernate andshutdown, may be often be confusing to end users who may have difficultydetermining which mode to use. In addition, resuming from standby to anormal operational mode may involve relatively fast processes—e.g., onthe order of seconds—but resuming from hibernate to normal operation maybe significantly slower by comparison. Although hibernate may consumemuch less power than standby, the time required to resume from hibernatemay be undesirable.

SUMMARY

In one aspect, a method for power state transitioning in an informationhandling system having a volatile memory and a nonvolatile memory isdisclosed. The method includes identifying dirty data in the volatilememory, wherein the dirty data includes data that has not been stored inthe nonvolatile memory. The method further includes writing dirty datafrom the volatile memory to the nonvolatile memory. The method furtherincludes transitioning to a reduced power state in response to a triggerevent and transitioning from the reduced power state in response to awake signal. The method further includes copying data from thenonvolatile memory to the volatile memory and waking an operating systemto a restored state.

In another aspect, a computer program, stored in a tangible medium forpower state transitioning in an information handling system having avolatile memory and a nonvolatile memory, is disclosed. The computerprogram includes executable instructions to cause at least one processorto: identify data in the volatile memory which has been modified or notpreviously stored in the nonvolatile memory; transfer modified or notpreviously stored data from the volatile memory to the nonvolatilememory; transition to a reduced power state in response to a triggerevent; transition from the reduced power state in response to a wakesignal; copy data from the nonvolatile memory to the volatile memory;and wake an operating system to a restored state.

In another aspect, an information handling system is disclosed. Aprocessor is communicatively coupled to a volatile memory and anonvolatile memory. A computer readable medium includes instructionsthat cause the at least one processor to: identify data in the volatilememory which has been modified or not previously stored in thenonvolatile memory; transfer modified or not previously stored data fromthe volatile memory to the nonvolatile memory; transition to a reducedpower state in response to a trigger event; transition from the reducedpower state in response to a wake signal; copy data from the nonvolatilememory to the volatile memory; and wake an operating system to arestored state.

Thus, the present disclosure provides apparatuses and methods forefficiently saving data and instructions, transitioning to one or morelow power states including mechanical off, and resuming from a low powerstate to normal operation with increased speed. The present disclosurealso enables elimination of the need to present a user with multiple‘off’ options. Other technical advantages will be apparent to those ofordinary skill in the art in view of the specification, claims anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIG. 1 is a block diagram showing an information handling system inaccordance with certain embodiments of the present disclosure;

FIG. 2 is a process flow diagram illustrating an operating systemmaintaining an image of system memory in fast nonvolatile memory inaccordance with certain embodiments of the present disclosure;

FIG. 3 is a process flow diagram illustrating shutdown storage processfor fast restart in accordance with certain embodiments of the presentdisclosure;

FIG. 4 is a process flow diagram illustrating a control transfer inaccordance with certain embodiments of the present disclosure; and

FIG. 5 is a process flow diagram illustrating a fast restart inaccordance with certain embodiments of the present disclosure.

DETAILED DESCRIPTION

For purposes of this disclosure, an information handling system mayinclude any instrumentality or aggregate of instrumentalities operableto compute, classify, process, transmit, receive, retrieve, originate,switch, store, display, manifest, detect, record, reproduce, handle, orutilize any form of information, intelligence, or data for business,scientific, control, or other purposes. For example, an informationhandling system may be a personal computer, a network storage device, orany other suitable device and may vary in size, shape, performance,functionality, and price. The information handling system may includerandom access memory (RAM), one or more processing resources such as acentral processing unit (CPU) or hardware or software control logic,ROM, and/or other types of nonvolatile memory. Additional components ofthe information handling system may include one or more disk drives, oneor more network ports for communication with external devices as well asvarious input and output (I/O) devices, such as a keyboard, a mouse, anda video display. The information handling system may also include one ormore buses operable to transmit communications between the varioushardware components.

Illustrative embodiments of the present invention are described indetail below. In the interest of clarity, not all features of an actualimplementation are described in this specification. It will of course beappreciated that in the development of any such actual embodiment,numerous implementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthe present disclosure.

For the purposes of this disclosure, computer-readable media may includeany instrumentality or aggregation of instrumentalities that may retaindata and/or instructions for a period of time. Computer-readable mediamay include, without limitation, storage media such as a direct accessstorage device (e.g., a hard disk drive or floppy disk), a sequentialaccess storage device (e.g., a tape disk drive), compact disk, CD-ROM,DVD, random access memory (RAM), read-only memory (ROM), electricallyerasable programmable read-only memory (EEPROM), and/or flash memory; aswell as communications media such wires, optical fibers, microwaves,radio waves, and other electromagnetic and/or optical carriers; and/orany combination of the foregoing.

FIG. 1 illustrates a block diagram of an example information handlingsystem 100, in accordance with certain embodiments of the presentdisclosure. In certain embodiments, information handling system 100 maybe a personal computer (e.g., a desktop computer, workstation orportable computer). As depicted in FIG. 1, information handling system100 may include a processor 105, a system memory 110 communicativelycoupled to processor 105, an I/O hub 115 communicatively coupled toprocessor 105, storage 120 communicatively coupled to I/O hub 115,nonvolatile memory 125 communicatively coupled to I/O hub 115, andfirmware 130 communicatively coupled to I/O hub 115.

Processor 105 may include any system, device, or apparatus configured tointerpret and/or execute program instructions and/or process data, andmay include, without limitation a microprocessor, microcontroller,digital signal processor (DSP), application specific integrated circuit(ASIC), or any other digital or analog circuitry configured to interpretand/or execute program instructions and/or process data. In someembodiments, processor 105 may interpret and/or execute programinstructions and/or process data stored in system memory 110, storagemedia 120 and/or another component of information handling system 100.Processor 105 may be coupled to other components (not shown) withoptional interfaces (I/Fs) via a PCIe (Peripheral Component InterconnectExpress) interface, for example.

System memory 110 may be communicatively coupled to processor 105, forexample, via a DDRn (a version of a double-date-rate type) interface.System memory 110 may include any system, device, or apparatusconfigured to retain program instructions and/or data for a period oftime (e.g., computer-readable media). System memory 110 may includerandom access memory (RAM), electrically erasable programmable read-onlymemory (EEPROM), a PCMCIA card, flash memory, magnetic storage,opto-magnetic storage, or any suitable selection and/or array ofvolatile memory. Note that apparatuses and methods described may applyto the volatile portions of system memory 110.

Processor 105 may be coupled to an I/O hub 115 via a host link, forexample. I/O hub 115 may be communicatively coupled to storage 120 via,for example, a small computer system interface (SCSI), Internet SCSI(iSCSI), Serial Attached SCSI (SAS) or any other transport that operateswith the SCSI protocol, advanced technology attachment (ATA), serial ATA(SATA), advanced technology attachment packet interface (ATAPI), serialstorage architecture (SSA), integrated drive electronics (IDE), and/orany combination thereof. Storage 120 may include computer-readable media(e.g., hard disk drive, floppy disk drive, CD-ROM, and/or other type ofrotating storage media, flash memory, EEPROM, and/or other type of solidstate storage media) and may be generally operable to store data and/orprograms (e.g., one or more operating systems and/or one or moreapplication programs).

I/O hub 115 may be communicatively coupled to firmware 130 via anysuitable interface such as SPI (System Packet Interface), LPC (Low PinCount) interface, for example. The information handling system 100 mayinclude one or more components that process and/or operate based onfirmware embedded in or coupled to the component. For example, suchcomponents may include hard disk drives (HDDs), CD-ROM drives, and DVDdrives, and/or various other devices and the like that includecontrollers driven by firmware. Firmware may be the program codeembedded in a storage device and maintained within or coupled to thedevice. The firmware for a component most often comprises theoperational code for the component.

More generally, firmware may include program code operable to control aplurality of information handling system 100 operations. System memory110, for example, may store firmware such as a basic input/output system(BIOS) program, and/or device drivers such as network interface card(NIC) drivers. A device driver may include program code operable tofacilitate interaction of a hardware device with other aspects ofinformation handling system 100. A BIOS program may include softwarethat facilitates interaction with and between the information handlingsystem 100 devices such as a keyboard, a mouse, and/or one or more I/Odevices. Information handling system 100 may operate by executing BIOSfor a system firmware in response to being powered up or reset. BIOS mayidentify and initialize components of system 100 and cause an operatingsystem to be booted.

I/O hub 115 may be communicatively coupled to nonvolatile memory 125 viaa PCIe interface, for example. Nonvolatile memory 125 may include, forexample, fast nonvolatile memory such as flash memory, NVDIMMs(nonvolatile dual in-line memory modules), a PCIe (Peripheral ComponentInterconnect Express) add-in-card, a direct connect nonvolatileinterface (e.g., an ONFI (Open NAND Flash Interface Working Group)interface), a SSD (solid-state drive), or another storage typeconfigured for fast restart. I/O hub 115 may be coupled to othercomponents (not shown) with optional interfaces (I/Fs) such as a PCIeinterface and device interfaces (I/Fs) such as a USB (Universal SerialBus) interface, for example.

In certain embodiments, an operating system may maintain a copy or imageof system memory 110 in fast nonvolatile memory 125. A page structuremay be used to keep nonvolatile memory current. A page may be a block ofmemory that may be virtualized such that there may be physical pages,virtual pages and a mapping function between them. An operating systemmay map physical memory to virtual memory and, beyond that, theoperating system may map physical memory to nonvolatile storage. A pagetable may be employed to store mapping between virtual memory andphysical memory. A translation lookaside buffer (TLB) may be utilized inconjunction with one or more page tables and, for example, may storepage table entries. An operating system may maintain a pool of availablepages. Upon initiation of a system process, the operating system mayallocate pages out of the available pool to that process.

In certain embodiments, all or some of the contents of system memory 110may be transferred to nonvolatile storage 125 on an opportunistic and/orincremental basis. It is to be understood that transferring data on anopportunistic basis means transferring data during idle periods or otherperiods of low system usage or low system component usage. For example,contents of system memory 110 may be transferred opportunistically.Access to sets of data and/or instructions stored in pages may includereads and/or writes as, e.g., in the case of R/W (read/write) pages. Anoperating system may maintain a record of whether or not a page has beenwritten to. A page in physical memory that has been written to maydiffer from its corresponding page in nonvolatile memory and accordinglybe deemed a dirty page. Dirty data may be volatile memory that has beenmodified. R/W pages may be checked during process idle periods for dirtytags, i.e., addresses to physical memory locations associated withmodified contents. After being identified, dirty pages may be stored tononvolatile memory during idle or other low-usage periods.

As an alternative to opportunistic transfer, contents of memory may betransferred on an incremental basis. It is to be understood thattransferring data on an incremental basis means transferring dataregardless of whether idle periods or other periods of low system orcomponent usage occur. For example, each time a page in physical memoryhas been written to, the contents of the page may be stored innonvolatile memory regardless of whether a system idle condition exists.One of ordinary skill in the art having the benefit of this disclosurewould understand that a number of variations may be employed to effecteither or both incremental and opportunistic transfer.

In some embodiments, an operating system may incorporate wear levelingwhen storing pages. The operating system may attempt to distribute thepages substantially evenly in nonvolatile memory and, thereby, avoid arelatively high concentration of write cycles. In some embodiments, anoperating system may communicate mapping to the firmware in a dedicatednonvolatile memory region. In some embodiments, an operating system maycreate mapping of the empty pages so that unallocated pages are notrestored upon a resume process, thereby increasing the speed of theresume process.

FIG. 2 shows a flow chart for one example of an operating systemmaintaining an image of system memory in fast nonvolatile memory. Atinitialization 200, the system is booted up in step 205. Immediatelythereafter, all records indicating whether pages have been stored innonvolatile memory may be initialized in step 210. For example, allpage_saved bits may be cleared. In step 215, initialization 200 may becomplete, and the system may then perform other operations.

Thereafter, process 220 may check and store page contents. At an idleperiod or other low-usage period, process 220 may begin at step 225. Instep 230, it may be determined whether a given page is dirty, e.g., bychecking a page_dirty tag associated with the page in the page table. Ifthe page is dirty, then in step 235 b the contents of the page may bestored in nonvolatile memory (NVM). A flag or other record may beupdated to reflect that the current instance of the page has beenstored. For example, a page_saved bit associated with the page may beset. The page_dirty tag must be reset (step 235 a) to prepare for thepossibility of another write. Also, an alternate copy of the tag may berecorded (step 235 a) for standard OS usage of the tag. If the page isnot dirty, step 235 may be skipped. Process 220 may continue to the nextpage in step 240 and repeat the process steps if the idle conditioncontinues. As an alternative to determining which pages have beenwritten to, process 220 may save pages on another basis, such as onrandom, prioritized, or sequential bases, during the idle period.

FIG. 3 shows a flow chart for one example of a shutdown storage process300 in support of a fast restart in accordance with certain embodimentsof this disclosure. At step 305, fast shutdown may be initiated by oneor more of a number of trigger events. One example is a single operatingsystem “off” function that may replace or be offered in addition tostandard standby, hibernate and shutdown options (or other multilevellow-power states) as user-visible options. Other examples may include apower button press, a laptop lid closure, a hot key, or a number ofvariations based on user preference and/or specific environments.Following the trigger event, all processes may be stopped in a mannersimilar to the current standby operation.

In steps 310 a and 310 b, it may be determined whether there is unsaveddata. For example, page_saved bits and page_dirty tags or otherflags/records may be checked to identify unsaved pages. Unsaved data maybe stored in nonvolatile storage, and associated flags/records may beupdated in step 315. In step 320, it may be determined if all pages havebeen checked. If all pages have not been checked, process 300 maycontinue to a next page at step 330 and loop to step 310. When all pageshave been checked, process 300 may end at step 325. Following a shutdownstorage process for fast restart such as process 300, preparation forfast restart shutdown may be complete. Control may be transferred tofirmware.

FIG. 4 shows a flow chart for one example of control transfer 400 inaccordance with certain embodiments of this disclosure. Control may betransferred from an operating system (OS) to firmware following a fastrestart shutdown command. Control transfer 400 may be initiated by afast restart shutdown request in step 405 when an operating system hasprepared for a restart from nonvolatile memory. In step 410, one or morehardware states may be saved. System firmware may store any additionaldata needed for further power reduction. For example, to enable a lowerpower state, additional information such as current PCIe configurationspace may need to be saved in certain configurations.

As would be understood by one of ordinary skill in the art having thebenefit of this disclosure, any number of variations may be made tomaintain power to certain system components and/or to prepare certainsystem components for any of a number of wake events, as desired. Forexample, it may be desirable for a configuration with access to ageneral purpose register to transfer the register information to fastnonvolatile memory. In other cases, it may be desirable to maintainpower to the register. Also for example, whether and what informationneeds to be saved may depend on core logic power well requirements of aparticular configuration, as would be understood by of ordinary skill inthe art having the benefit of this disclosure.

In step 415, a flag or other record may be updated to reflect that thesystem has been prepared for a fast restart. For example, afast_restart_ready flag may be set in firmware. In some environments, itmay be desirable to allow for one or more wake events in step 420. Powercontrol may be set to support resume events, for example, to allow wakeon LAN and/or other wake events. Process 400 may end at step 425 withthe system entering a reduced power state.

FIG. 5 shows a flow chart for one example of fast restart 500 inaccordance with certain embodiments of this disclosure. In step 505, anyof a number of wake events occurs. For example, a wake event may beuser-initiated. In step 510, a flag or other record—e.g., thefast_restart_ready flag—may be checked to determine whether the systemhas been prepared for a fast restart. If the system has not beenprepared for a fast restart, fast restart 500 ends in step 515, and thesystem may be configured to proceed with another process such as a freshboot, as desired. If the system has been prepared for a fast restart,one or more of the hardware states that were stored in control transfer400 may be restored to previous states, as needed, in step 520. At thatpoint, the operating system may not be active and may not be able torestore its state. In step 525, contents of nonvolatile memory (NVM) maybe copied to system memory, which, for example but not by way oflimitation, may be DRAM. Copying contents of the nonvolatile memory backto the system memory may enable the operating system to return to aprevious state. In some embodiments, firmware may recreate tables, suchas multiprocessor tables, PCI enumeration tables, and/or other tables,as in a full reboot or resume. In other embodiments, firmware may havesaved some of the tables the first time they are created intononvolatile memory rather than recreating the tables on a fast restart.In step 530, a flag or other record, such as the fast_restart_readyflag, may be reset.

Fast restart 500 may additionally include, in certain embodiments,determining whether or not certain wake events require control to bereturned to the operating system, depending on the whether the system iscapable of operating without waking the operating system. In someembodiments, it may be determined at step 535 whether an out of bandwake condition requires fast restart 500 to end at step 540 andtransition to out of band system management, for example. Absent such acondition, fast restart 500 continues to step 545, where firmware wakesthe operating system to a restored state and transfers control to theoperating system.

In certain embodiments, compression may be used to increase processspeed and minimize nonvolatile memory requirements. For example,compressed data may be stored in nonvolatile memory, and another mediumsuch as the hard drive may be used for overflow. Upon restart, certainpages may be retrieved from the hard drive rather than nonvolatilememory.

In certain embodiments, a map (e.g., a bit per page to indicate thepresence of information) of occupied physical pages may be maintained bythe OS and passed to the firmware. This map would be saved innonvolatile memory and used to reduce the amount of date transferredduring fast restart.

Thus, the present disclosure provides apparatuses and methods forefficiently saving data and instructions, transitioning to one or morelow power states including mechanical off, and resuming from a low powerstate to normal operation with increased speed. The present disclosuremay also enable elimination of the need to present a user with multiple‘off’ options. Other technical advantages will be apparent to those ofordinary skill in the art in view of the specification, claims anddrawings.

Although the present disclosure has been described in detail, it shouldbe understood that various changes, substitutions, and alterations canbe made hereto without departing from the spirit and the scope of theinvention as defined by the appended claims. Various changes,substitutions, and alterations can be made to interfaces with multipledevices at one end and a single device at the other end withoutdeparting from the spirit and the scope of the invention.

1. A method for power state transitioning in an information handlingsystem having a volatile memory and a nonvolatile memory, the methodcomprising: identifying dirty data in the volatile memory, wherein thedirty data comprises data that has not been stored in the nonvolatilememory; writing dirty data from the volatile memory to the nonvolatilememory; transitioning to a reduced power state in response to a triggerevent; transitioning from the reduced power state in response to a wakesignal; copying data from the nonvolatile memory to the volatile memory;and waking an operating system to a restored state.
 2. The method ofclaim 1, wherein the writing dirty data is performed on an opportunisticbasis.
 3. The method of claim 1, wherein the writing dirty data isperformed on an incremental basis.
 4. The method of claim 1, wherein:the transitioning to the reduced power state includes saving dataassociated with one or more hardware states to the nonvolatile memory;and the transitioning from the reduced power state comprises includesrestoring the one or more hardware states based, at least in part, onthe data associated with the one or more hardware states.
 5. The methodof claim 1, further comprising: transferring control of thetransitioning to firmware.
 6. The method of claim 1, wherein thenonvolatile memory is a flash memory.
 7. The method of claim 1, whereinthe nonvolatile memory is an SSD.
 8. A computer program, stored in atangible medium for power state transitioning in an information handlingsystem having a volatile memory and a nonvolatile memory, comprisingexecutable instructions to cause at least one processor to: identifydata in the volatile memory which has been modified or not previouslystored in the nonvolatile memory; transfer modified or not previouslystored data from the volatile memory to the nonvolatile memory;transition to a reduced power state in response to a trigger event;transition from the reduced power state in response to a wake signal;copy data from the nonvolatile memory to the volatile memory; and wakean operating system to a restored state.
 9. The computer program ofclaim 8, wherein the computer program further comprises executableinstructions to cause the at least one processor to: transfer modifiedor not previously stored data from the volatile memory to thenonvolatile memory on an opportunistic basis.
 10. The computer programof claim 8, wherein the computer program further comprises executableinstructions to cause the at least one processor to: transfer modifiedor not previously stored data from the volatile memory to thenonvolatile memory on an incremental basis.
 11. The computer program ofclaim 8, wherein: the transitioning to the reduced power state comprisessaving data associated with one or more hardware states to thenonvolatile memory; and the transitioning from the reduced power statecomprises restoring the one or more hardware states based, at least inpart, on the data associated with the one or more hardware states. 12.The computer program of claim 8, wherein the computer program furthercomprises executable instructions to cause the at least one processorto: transfer control of the transitioning to firmware.
 13. The computerprogram of claim 8, wherein the nonvolatile memory is a flash memory.14. The computer program of claim 8, wherein the nonvolatile memory isan SSD.
 15. An information handling system, comprising: a processorcommunicatively coupled to a volatile memory and a nonvolatile memory; acomputer readable medium comprising instructions that cause the at leastone processor to: identify data in the volatile memory which has beenmodified or not previously stored in the nonvolatile memory; transfermodified or not previously stored data from the volatile memory to thenonvolatile memory; transition to a reduced power state in response to atrigger event; transition from the reduced power state in response to awake signal; copy data from the nonvolatile memory to the volatilememory; and wake an operating system to a restored state.
 16. Theinformation handling system of claim 15, where the instructions furthercause the at least one processor to: transfer modified or not previouslystored data from the volatile memory to the nonvolatile memory on anopportunistic basis.
 17. The information handling system of claim 15,where the instructions further cause the at least one processor to:transfer modified or not previously stored data from the volatile memoryto the nonvolatile memory on an incremental basis.
 18. The informationhandling system of claim 15, wherein: the transitioning to the reducedpower state comprises saving data associated with one or more hardwarestates to the nonvolatile memory; and the transitioning from the reducedpower state comprises restoring the one or more hardware states based,at least in part, on the data associated with the one or more hardwarestates.
 19. The information handling system of claim 18, wherein theinstructions further cause the at least one processor to: transfercontrol of the transitioning to firmware.
 20. The information handlingsystem of claim 15, wherein the nonvolatile memory is an SSD.